Film driving apparatus



Feb. 1l, 1947. a R, w. BENFER 2,415,406

FILM DRIVING APPARATUS Filed latch 8, 1944 /NVE/VTOR R. W BENFER A T TORN V Peienied Feb. 11, 1947 UNITI-:D STATES PATENT OFFICE FILM DRIVING APPARATUS Richard W. Beniel', Morristown, N. J., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 8, 1944, Serial No. 525,623

' direction of travel of the film through the ape paratus.

y It is a further object of this invention to provide a reversible film driving apparatus in which the sequence of engagement of the film with the driving and guiding elements is the same for either direction of travel of the lm.

A feature of the invention resides in a novel arrangement of film driving and guiding elements permitting a method of film threading which places the constant 'speed film driving sprocketon the'take-up side of the lm guid' ing means at the film exposure point for either direction o f travel .cf the film.

Specifically, in accordance with-the invention,

1 the lm is supported at the exposure point by .ing is realized in which the iilm is engaged and driven in the proper direction from the take-up side of the drum by the constant speed sprocket" without interference with the lm loop from the driving sprocket to the feed side of the drum for either direction of travel of the film. I In the arrangement of elements in accordance with thel invention, the constant speed sprocket is disposed between the drum and driving sprocket with its axis lying substantially in a plane including the. axes of the drum and driving sprocket. The constant speed sprocket diameter is so chosen that the driving teeth on the periphery thereof lie within the space bounded by two planes each of which is commonly tangent to the drum and driving sprocket, onel above and one below the plane including the axes of the drum and driving sprocket. While the drawing discloses the drum diameter as being larger than either sprocket, either the drum diameter or the driving sprocket diameter or both may be larger than the diameter ofthis constant speed sprocket to maintain the condition set forth.

The invention may be more readily understood by reference to the accompanying drawing in which:

Fig. 1 is an elevation of a recording film driving apparatus showing the method of lm threading for forward direction of film travel through this apparatus; A

Fig. 2 discloses a negative film bearing a sound track recorded in the apparatus of Fig. 1;

Fig. 3 shows a positive print madev from the lfor reverse direction of iilm travel-through the apparatus; and

Fig.A 5 discloses a reversal developed positive of a negative bearing a sound track recorded thereon in the apparatus as disclosed in Fig. 4.

In direct recording of 16 millimeter sound film it is at times desirable to obtain a sound negative which may be given a standard development and a number of positive prints obtained therefrom. At other times it is desirable only to obtain a sound negative from which the positive print may be obtained by reversal Vdevelopment of the negative. As 16 millimeter sound negative film is provided with but one row of sprocket perforations and in the usual recording process is propelled through the recording apparatus always in the same direction, the relative position of the sound track and marginal sprocket perforations will not be the same on the reversal developed positive as on the positive print obe tained from the developed negative. This condition will obviously introduce diiiiculties in the subsequent sound reproduction or processes employed in combining picture and sound on the same film.

This difficulty may be overcome by propelling the-recording lm through a recording apparatus in one direction, starting from one end of the film roll for a resulting reversal developed positive and in the opposite `direction starting from the other end of the illm supply roll for a resulting positive printed from a developed negative. In this manner the relative position of the sound track and the marginal film perforation aeiaeoe tained in present sound film recording apparatus by film driving mechanism including a rotatable lm supporting drum at the exposure point, a constant speed sprocket engaging the lm on the take-up side of the drum, and a feed and takeup sprocket for drawing the film from the supply reel and feeding the film to the take-up reel. To obtain equal uniform speed of fllm in either direction of travel through a reversible film driving apparatus, the same sequence of engagement of the film with the driving elementsshould be realized for either direction of travel of the nlm, that is, the film should be engaged by the constant speed sprocket on the take-up side of the drum for either direction of film travel. nThis desirable film engaging sequence cannot be realizedwith existing sound lm driving apparatus because no method of'film threading to produce this result can be realized without producing interference between the film loops on the feed and `take-up side of the film supporting drum.

Referring to Fig. 1, the sound film recording apparatus shown therein comprises a housing I havingan opening 2 for the admission of a recording light beam and openings 3 and 4 for the admission and exit of a recording lm F from supply reel to take-up reel 6, respectively. The film F is drawn from supply reel 5 and fed to take-up reel 6 by sprocket 1 mounted on shaft 8. A gear 9 secured to shaft 8 is driven by a worm gear I0. The hn is supported at the exposure aperture by a rotatable drum II. This drum ,is secured to a shaft I2 which is rotatable in suitable bearing's. In the usual construction, an inertia device such as the fiy-wheel is secured to this ishaft to be rotatable with the film driven drum II.

A constant speed sprocket I3, mounted on shaft I4 engagesV and drives the film towards sprocket 1 from the take-up side of drum I I. Sprocket I3 is rotated in a direction opposite to the direction of rotation of sprocket 1 by means of a worm gear I5 in engagement with gear I6. In the usual construction of apparatus of this type the means areprovided usually in the form of a resilient coupling between the gear I6 and shaft I4 to insure constant rotational speed of sprocket I3.

LThe gear I0 for sprocket 1 and the gear I5 `for' sprocket I3 are mounted on a shaft I1 having one end rotatable in a suitable bearing I8 vand the other end coupled to a reversible electric motor I 9.

A sound recording optical system includes a constant light source 20, a condenser lens 2I, a

light valve or other light modulating device 22,

' and an objective lens unit 23 extending into the may be different from that shown in the drawing,

that is, this sprocket may be placed nearer the sprocket 1 or nearer the drum II so long as its diameter is such that the driving teeth on the peripheral surface thereof do not extend beyond planesindicated by lines 25 -and 26, each plane beinga common tangent to drum I I and sprocket I1, one above 'and one below, respectively, the plane indicated by line 24.

' The methodl of film threading in the direction of travel of the lm through the apparatus as shown in Fig. 1 is employed when the resultingl .'from the negative of Fig. 2 and in which in the printing operation the emulsion side of lthe positive faces the emulsion side of the negative.

It will be seen that the relative position of the single row of sprocket holes and the sound track as viewed from the side of the film bearing the emulsion is different from the films of Figs. 2 and 3. Therefore, if in one case the positive of a sound record lmrecorded in the apparatus of Fig. 1 were to be obtained by a reversal development of the film in Fig. 2 and in another case by a printing operation from the developed negative of Fig. 2, the relative position of the sound track and the marginal sprocket perforation on the two lms would be such that one of these films would have to be propelled through a reproducing apparatus with its emulsion side reversedto bring the sound track in registration with the sound reproducing optical system. Fig. 4 discloses the same machine as disclosed in Fig. 1 but with the lm threaded over the guidin-g and driving elements for reverse travel of the nlm therethrough starting from the opposite end y lof the film roll so that the emulsion side of the recording film is presented to the light beam as before and the non-perforated marginal edge of the film passes through the recording light beam. The same sequence of lm engagement with the guiding and driving' elements is obtained for either direction of travel, that is, the lm path for either direction extends from the feed side of -sprocket 1 to drum I I, thence over the side of noted that the relative position of the soundl track and the marginal perforation isv the same in both the positive sound films shown in Fig-3 and Fig. 5.

By means of the machine described herein and with a knowledge of the type of development to be subsequently employed in obtaining a positive, the direction of travel through the machine may be chosen so that there will result a positive in which-the sound track will be in the correct relative position to the marginal sprocket perforations. By reason of the uniformity in film speed obtainable in the recording machine disclosed herein, efficient uniform sound recording on each record is assured regardless of its direction of travel through the apparatus.

What is claimed is: 1. In a driving apparatus for propelling a lm strip past an exposure point, a pair of film magazines, a driving sprocket for drawing said film stripfrom one of said magazines and feeding said illm strip to the other of said magazines, a rotatable support engaging said film adjacent an exposure point, a second sprocket disposed between said iirst sprocket and said rotatable support with its axis substantially in alignment with the axes of said support and said first sprocket, driving means producing rotation of said sprockets in opposite directions, said driving means being reversible to reverse the direction of rotation of said sprockets'the lm path for either di" rection of operation extending from one side of said illm sprocket to said support, thence over a side of said second sprocket adjacent the film path from said first sprocket to said support, and thence to the other side of said first sprocket, whereby said lm strip is in driving engagement with said second sprocket on the take-up side of said rotatable support' for either direction of travel of said lm strip through said apparatus.

2. In a film vrecorder driving apparatus for propelling a recording nlm strip past an exposure point with equal uniform speed in either forward or reverse direction of travel through said appasurfaces located between two planes each ofwhich is a common tangent to said drum and said first sprocket, one above and one below a plane including the axes of said drum and first sprocket,

whereby said lm strip may be engaged and driven in the proper direction by said second CII sprocket from the take-up side of said drum in either direction of rotation without interfering with the free travel of said film strip from said first sprocket to the feed side of said drum.

3. A 111m driving apparatus for propelling a iilm strip past an exposure point in two directions with said film strip having the same sequence o! engagement with the driving elements of said `apparatus for either direction of travel, comprising a rotatable dilm supporting drum, a first sprocket for feeding said film to and drawing said film from said drum, a constant speed.

' sprocket, means for drivingvsaid sprockets in opposite directions. said driving means being reversible to reverse the direction of rotation of each of said sprockets, said constant speed sprocket having a. diameter smaller than either RICHARD W.

REFERENCES crrnn y -vThe following references are of recordin the ille of this patent:

UNITED STATES PA'IENTS Number Name Date 1,802,595 De Forest Apr. 28, 1931 2,036,584 Kuppenbendei` Apr. '7, 1936 2,266,755

Herzig Dec. 23, 1941 

